|One of the distinctive skull structures of the carnivorous marsupial, the Tasmanian tiger, was its large gaping jaw. This powerful feature also led to another nickname, the marsupial hyena, because it shares that strong skull structure with the dog-like hyena in Africa.|
According to the World Wildlife Fund, the Earth is losing species at a rate not seen for 65 million years, since the extinction of the dinosaurs.
The study of biodiversity and astrobiology share the common thread of viewing the planet as a whole and attempting to see its future by examining its past. The present moment in history has been characterized as the first time in which one species– humans– are in one way or another ‘responsible’ for the entire biosphere: changing it, maintaining it, and of course, possibly extinguishing it. As Harvard professor of evolutionary biology , Andrew Knoll, remarked: " [For astrobiology] everything we know about life in the universe comes from life on Earth. In a sense, putting current diversity at peril for those who would like to understand biology as a planetary phenomenon is like burning a library."
In modern history, one of the most remarkable stories of human responsibility for biodiversity centers on Australia, and in particular, the fate of a class of species unique to that continent, the marsupials (or pouched animals). A January 2003 expedition of travel writers and artists dispatched to the Australian state, Tasmania, went in search of remnants and reflections of what many believe is an extinct animal – the Tasmanian tiger. Their forthcoming book, entitled Ghost Hunters: On the Trail of the Tasmanian Tiger, will survey the findings of their trip and frame many of the key questions about biodiversity: How do species evolve under environmental and human pressure? How does loss of one species affect others? How do we measure and monitor the changes as they occur?
Tasmania has seen barely two centuries of outside human influences. Large parts of the island still look today the same as when Charles Darwin or Captain Bligh first sailed to its coasts. Prior to when the waters of the Bass Strait cut the island off from Antarctica, Tasmania was the only land bridge between Australia and the South Pole. In fact Antarctica, Australia, New Zealand, Africa, South America and India were once part of a supercontinent called Gondwana . About 100 million years ago, it broke apart, and the land masses slowly drifted into their current positions.
But the remarkable array of Tasmania’s native wildlife – the famous Tasmanian devils, kangaroos and the Tasmanian tiger — lived and evolved in isolation. Indeed, the deep Australian waters prevented continental transfers of animals, and when isolated expeditions returned from Australia to England, great scientific controversies broke out over the authenticity of their preserved specimens. Thought to be hoaxes or taxidermist’s tricks, the marsupials particularly seemed to be pasted together from pieces of known animals found elsewhere (like the platypus with its ‘beaver-like tail’, duckbill, and mammalian rearing of young).
The Tasmanian tiger, or thylacine (Thylacinus cynocephalus), was the only species of the marsupial family Thylacinidae to have existed within historical times. It is sometimes referred to as the Tasmanian wolf but as a marsupial, is neither a tiger nor a wolf. The distinction derives mainly from its placental pouch -rearward facing, unlike a kangaroos- where its young pups matured for their first 3 months. But even the name for the Tasmanian tiger, or thylacine, is an example of what fascinates evolutionary biologists. The tiger is regarded as a perfect example of the principle of "convergent evolution".
|Thylacene (standing), soil from clear hill road near lake gordon and acrylic polymer on paper, click image for larger view, or view slideshow |
Credit: Alexis Rockman, Copyright 2003
Convergent evolution is the process by which a living thing, over the course of its evolution, comes to physically resemble another life form. This occurs as a result of adaptation to similar environments and ways of life. The thylacine’s body shape resembles that of the placental wolf because it too is a cursorial predator which lives and hunts in much the same way. Its short, thick coat is striped, like a tiger’s, since its largely lush jungle homeland shares many features with the Indian subcontinent where the large cats also developed a striped coat.
With its long tail stretching nearly a third of its total body length, the tiger shared the characteristics of other marsupials like kangaroos. Its powerful tail comprised 25 individual vertebrate. Most descriptions indicate that the slow, stiff predator had a body type distinctly unsuited to the chase: its likely pattern of pursuit was marked by a marathon, rather than a sprint, as it tirelessly pursued its targeted wallabies, small mammals and birds to their exhaustion and death.
Although it vocalized infrequently through what was considered a kind of whining yelp, the tiger’s large gaping jaw–the largest proportionally of any mammal–presented a fiercesome set to teeth specialized to the small game it captured. Indeed, unlike African predators which strangle their prey, the Tasmanian tiger was thought to use its massive jaws not to suffocate its prey at the vulnerable throat, but rather violently to crush the skull of its quarry.
According to fossil remains, the tiger roamed a wide area on the main Australian continent until at least 3,000 years ago, and then in historical times was only found in Tasmania. When immigrants from Asia first moved to Australia, it is believed that the introduction of a domestic species, the dog, brought competitive pressures on the tiger population, particularly when the dog population grew and indigeneous feral (dingo) hunting packs reduced the local game. But until the 18th and 19th century, Tasmania remained a refuge of sorts, prior to the introduction of European settlers and their sheep herds.
Hunted to Extinction
Sheep-herders largely considered the Tasmanian tiger to be a pest or threat to their livelihoods. Whether truly preying on sheep in the numbers reported, or whether thieves and dingos were equally culpible, the Tasmanian government set a bounty for hunting down the tigers in large numbers. Quickly driven from its nocturnal hunting patterns in open grasslands and forests, the last remaining tigers were seen in only the densest rainforests – much like the currently threatened Asian tigers.
Culling of the Tasmanian tiger population began intensely in the early 1800′s, and continued apace until the 1840′s, when its habitat had shrunken to the highlands and thick jungles. In addition to these tiger hunting parties, trapping, poisoning, and dog competition led to the last known wild tiger being killed in 1930.
The very last captive animal (Benjamin) died at the Hobart Zoo on September 7, 1936 –the same year that the Tasmanian government issued legal protection to discourage their destruction.
Since 1936, the tiger has come to represent a violent relationship between the wilderness and civilization. Although officially declared extinct only in 1986, 50 years after the last known individual died, anecdotal accounts of tiger sightings continue to build the folklore surrounding the tiger’s history. "Many local Tasmanians claim sightings of the tiger," said Dr. Lisa Hill, a Tasmanian native and now Political Science Professor associated with the University of Adelaide. "But people prefer to keep such sightings quiet out of fear that poaching even that one last enclave –if it exists — might begin anew."
Interview with the Expedition Team: Alexis Rockman
Artist Alexis Rockman, participated in the recent Tasmanian expedition, and created his unique illustrated account of the Tasmanian wildlife for the forthcoming Ghost Hunters book. Astrobiology Magazine editors had the opportunity to interview the New York-based painter as he created his personal portrait of what the expedition offered as lessons on biodiversity.
As the online InDepth Art News introduced Rockman for his gallery show "Future Evolution", his artistic interests have long centered on such questions of biodiversity: "Alexis Rockman’s meticulous paintings of naturally or artificially mutated creatures are information-rich depictions of the effect the human race has had – and will have – on the planet, especially on plants and animals. Rockman casts dark predictions of the role that humans play in determining the future course of natural history. Simultaneously straddling science and art, fantasy and reality, as well as beauty and the grotesque, Rockman’s work has been described as Hieronymus Bosch meets science textbook illustration."
|Postcard of Tasmanian Marsupial Wolf. Hobart Zoo c. 1928. Credit: G.P. Whitley Papers Australian Museum Archives|
Astrobiology Magazine (AM): How did the title, "Ghost Hunters", first come about?
Alexis Rockman (AR): The title "Ghost Hunters" refers not only to the extinct (?) thylacine, but its historical memory and the way it’s perceived by culture.
AM: How did you first become interested in the expedition to Tasmania?
AR: I have made images to accompany the text that are derived from materials that have a relationship to the images in the drawings (ie. soil, kelp, bark, and other organic material). [see gallery slideshow]
AM: Can you describe the current setting? Is it dense forest, and can you relate any reactions of the crew to your surroundings?
AR: Tasmania is incredibly diverse, and it is primarily an island ringed with temperate rainforest, including everything from buttongrass plain to alpine mountainous habitat.
AM: About the Tasmanian tiger, what lessons can be learned for species’ diversity and conservation, based on your previous interest in this area artistically?
|Westell 1910. The Book of the Animal Kingdom. Mammals. fig.159|
AR: I’ve spent my career pondering the history and plight of animals and plants that have gone extinct within recent historical memory.
AM: Do any of those you encounter in the Tasmanian wildlife conservation groups offer their opinions or insights on the current expedition or efforts in the future to understand the complex inter-relationships of one species to others in the competition for resources?
AR: Tasmania, like the rest of the world, has an innate tension between the resources humans feel entitled to and relentlessly pursue, and habitat needed to sustain biodiversity.
AM: Where are you in the timeline for the expedition now?
AR: The expedition is now an internal one, from my studio.
AM: What will your follow-up schedule look like when you return? Plans for the future?
AR: I’m currently exhibiting 8 of the drawings at my New York Gallery, Gorney, Bravin + Lee. The show is up through April 19. I also have other things in the works.
An extinct species that ironically received protection in the same year that its last known survivor died has a short epilogue. There are instances of sightings in Tasmania that crop up occasionally, but there are even more surprising endings in store for the tiger mythology.
On September 7, 1999 – 63 years to the day after Benjamin, the last captive tiger died – an ambitious project funded by the Rheuben Griffiths Trust was announced. The project will attempt to resurrect the species. The Trust and the Australian Museum are providing research into cloning the tigers by harvesting pup cells that were preserved in alcohol. In May 2002, DNA fragments that were both unmistakably from the tiger and that were undamaged enough to provide a potential working model in cells for DNA amplification became available. The project has plans for the first live tiger birth sometime around 2010 –and if successful, would represent the first cloning of an extinct species ever completed.
In September 2004, Villard, a division of the Random House Trade Group, will publish GHOST HUNTERS: On the Trail of the Tasmanian Tiger by Michael Crewdson and Margaret Mittelbach with illustrations by Alexis Rockman. Rockman previously provided 37 images to Peter Ward’s book, Future Evolution: An Illuminated History of Life to Come.
Related Web Pages
, Future Evolution: An Illuminated History of Life to Come.
Biodiversity: Interview with Andrew Knoll Part I
Extinctions: Interview with Andrew Knoll Part II
Genetic Engineering and Human Intervention: Part III
Accounts of Sightings
Australian Museum Online: To Clone or Not to Clone?
Thylacine tales SMH
Tasmania PWS – Thylacine
Environment Australia – Fact sheet
University of Tasmania – School of Zoology